System Approach to Air‐gun Array Design *

Abstract

To specify intelligently a nondynamite source in a marine seismic data‐collection system, it is important to use all known parameters of the system—source, receiver, and recording‐system characteristics. A technique has been developed to design the far‐field pressure pulse of an air‐gun array by taking these parameters into account. Important source variables to consider are interaction among guns in the array and the depth of the array. Near‐field pressure signatures of individual guns, which are relatively unaffected by boundaries, have been used to‘construct’the far‐field pressure pulse of the array by considering these variables. Comparison between constructed pulses and measured far‐field pulses shows substantial agreement. Streamer depth and recording‐system bandpass should also be considered when designing an air‐gun array. Comparison of far‐field pressure pulses for several bandpasses clearly shows the importance of considering this variable; e.g., the initial pulse is severely attenuated when a high‐cut filter is used. Likewise, an additional filtering effect due to the streamer's proximity to the surface should be taken into account. Design of an air‐gun array using the principles just outlined are illustrated by an example.

Signatures From Single Airguns*

“…For the amplitude A there is a reasonably good fit to the theoretically predicted relation A K V1/3. This result is also in agreement with the experimental relation found by Giles and Johnston (1973) and Johnston (1980). The variation in primary-to-bubble ratio R ( fig.…”

Influencing factors of seismic signals generated by un-tuned large volume airgun array in a land reservoir

“…Figure 4 shows the variation of the amplitudes (A) of airgun signals with firing pressures (P). Results from previous oceanic experiments indicate that the amplitudes are exponentially proportion to the pressures A / P (Giles and Johnston 1973;Dragoset 2000), A / P 0:551 (Johnston 1980) or A / P 3=4 (Vaage et al 1983). Therefore, in this study, we use the function A ¼ kP x to fit our data.…”

“…Seismic signals and their influencing factors for ocean used airgun array have been intensively studied since the 1960s (Kramer et al 1968;Giles and Johnston 1973;Nooteboom 1978;Johnston 1980;Vaage et al 1983;Langhammer and Landro 1993a, b). The empirical relations between these factors and the characteristics of airgun signatures (e.g., the amplitude of primary pulse, the period of bubble pulse and the primary-to-bubble amplitude ratio) have already been drawn.…”

Measurement of Airgun Waveforms

“…The use of a waveform in synthetic seismic reflection profiling modelling will be presented in a future paper. Attempts have been made to measure airgun waveforms (Giles 1968;Ziolkowski 1970;Mayne & Quay 1971;Schulze-Gatterman 1972;Giles & Johnston 1973) but these are not considered to satisfy adequately all the requirements: known impulse response of the recording system, adequate depth of water so that bottom reflections do not interfere with primary arrivals, known geometry of gun and receiver, and measurement at a sufficient depth to measure the downgoing wave into the sea bed. These effects are considered separately.…”